In recent years in the development of computer technology, the alphanumeric keyboard has been augmented by input devices which are used to position the cursor on a monitor screen for selecting icons by the operation of a switch. The most common such input device is the mouse. Hardly a personal computer today is found without a mouse or other pointing device which allows the mouse or pointing device to control certain functions of the computer.
The mouse, being a hand operated device used on the horizontal work surface near the keyboard and monitor, must be connected by a cable which unfortunately limits the range of the movement of the mouse. The cable which supplies operating power to the mouse also receives signals from the mouse about its position and user commands.
The mouse typically includes a ball which rolls on a surface or mouse pad. The ball is coupled to optical chopper wheels within the mouse housing which respond to movement of the mouse to produce pulses of light representing mouse movement. This is all well known conventional mouse technology.
Inside the mouse, electrical power, is converted to light by four light emitting diodes (LED's), two each at two orthoginally-oriented chopper wheels. As the mouse is moved on a surface, the chopper wheels rotate in correspondence with the lateral or longitudinal components of motion of the mouse. Light is intermittently blocked by spokes of the chopper wheels, or projected through the holes in the chopper wheels, where it is detected by the photo detectors within the mouse and converted back to electrical signals representing mouse movement. Command signals are usually in the form of switch operations by the user. Mice heretofore have been electro/optical/mechanical devices.
It would be highly desirable to provide a mouse or other pointing device which performed the same functions but without a cable connection to the computer. Several attempts have been made to accomplish this objective but none have met wide success.
Some cordless mice have been developed which communicate with the computer with an infrared or radio signal generated in the mouse, similar to appliance remote controls; however, all have also been electro/optical/mechanical devices, in which internal batteries provide an electrical charge for a limited time before they must be recharged, interrupting use of the computer and inconveniencing the user. Further, batteries add weight to the mouse and increase the mass and inertia, causing fatigue to the computer user. While cordless mice eliminate the inconvenience and restrictions of a cord, they nevertheless are heavier, more complicated and more expensive than corded mice.
There also exists a continuing need for improved low cost optical systems which use a minimum of refractive elements, e.g., lenses or prisms. In connection with meeting the need of a low cost cordless purely reflective computer mouse, it is also an objective of this invention to produce a general purpose optical system totally devoid of refractive elements.